Positioning system and method

ABSTRACT

A positioning system for locating objects in places where standard Global Position System signals do not penetrate. A first embodiment uses a GPS receiver and a clock recovery unit. A computer receives the positional information and accurate time information. The computer calculates new orbital data for at least four pseudosatellites. The pseudosatellites are antennas positioned in an interior or shielded space and function to send pseudosatellite data to a receiver. In a second embodiment, the positions of the pseudosatallites are provided to the computer without the use of a GPS receiver. An accurate clock signal is also provided. The computer calculates orbital data for each pseudosatellite and transmits the time signal and ephemeris data for each pseudosatellite. The time signal is delayed for each pseudosatellite to account for propagation delays due to different connecting cable lengths.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to positioning or location systemsand, in particular, to such a system as utilized to locate objectswithin an interior space or shielded environment. More specifically, butwithout restriction to the particular embodiments hereinafter describedin accordance with the current best mode of practice, this inventionrelates to a location positioning system for use in a shieldedenvironment that utilizes GPS-type signals.

2. Discussion of the Related Art

The art of proximity detection and position location has beencontributed to by a number of proposed devices and systems. Theseinclude, for example, the device discussed in U.S. Pat. No. 5,311,185 toHochstein et al. which is directed to a proximity detection devicerelying on a transponder that periodically transmits status signals.Transceivers are fixed at locations about a structure for receiving andtransmitting signals. U.S. Pat. No. 5,363,425 to Mufti et al.incorporates an identification badge having a radio frequency (RF)transmitter. Radio frequency (RF) receivers are located in telephones invarious rooms of a structure. The location of the identification tag isdetermined to be the room with the nearest phone. Anders et al. in U.S.Pat. No. 4,656,463, propose a passive transceiver tag which is sensed byan active transceiver. This proximity control system forms the basis fora location, identification, and measurement of movement of inventorysystem, commonly referred to as a LIMIS system.

Prior devices and systems, as exemplified by those discussed above, havebeen directed to the use of proximity detection. Typically, thesedevices use a radio frequency (RF) transponder and a radio frequency(RF) receiver. Proximity is measured by detection of a signal or bysignal strength. Current proximity devices, therefore, lack the abilityof precisely measuring the location of an object.

One current type of location position system does, however, offer theadvantage of precise location. Such an existing system is known as theGlobal Positioning System (GPS). This system includes a number ofsatellites in orbit around the Earth. Each satellite produces acontinuous signal which carries both a time component and a spacecomponent having a number of orbital parameters associated therewith. AGPS receiver, employed in conjunction with an appropriately programedcomputer, is used to receive at least four of the satellite signals andtherefrom determine a precise location of the receiver. This locationinformation is typically presented as longitude, latitude, and altitude.One critical limitation of the GPS is that it requires the satellites tobe "in view" relative to the receiver. This means that no obstructioncan exist between the minimum number of satellites and the receiver. Thestandard GPS, therefore, will not function inside a building since theGPS signal is blocked by glass, metal, foliage, soil, brick, and variousother materials which cause deflection of the signal. The GPS signal isoptimally employed in an environment such as a flat desert or on thehigh seas. Thus, while the GPS has many important uses in wide openspaces, it is not currently available for use within interior spaces orshielded environments.

In addition to the U.S. patents discussed above, other relatedreferences deal exclusively with outside signals. Such referencesinclude, for example, U.S. Pat. No. 5,051,741 to Wesby; U.S. Pat. No.5,334,974 to Simms et al.; and U.S. Pat. No. 4,918,425 to Greenberg etal.

Positioning systems are becoming widely recognized as being moreimportant in today's society. There is a current need in business andindustry to precisely locate and/or track the movement of people andmaterial assets such as inventory or capital equipment. Structures suchas the World Trade Center or large factories, which can employ thousandsof people, currently desire the ability to locate people who may requireassistance in reaching their intended destination. This is also true forlarge theme or amusement parks and other expansive tourist areas. Inaddition, this current need generally applies to people, objects, andinventory whether they may be located indoors, out-of-doors, or movingtherebetween. The prior art devices and systems discussed above do notmeet these needs because they lack precision or are currently incapableof operating within shielded environments or interior spaces.

Thus, prior to the present invention disclosed herein below, there hasnot been proposed a positioning system that precisely locates an objector person by utilizing GPS or GPS-type signals in an interior space orshielded environment.

OBJECTS AND SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to improve positionlocation systems.

Another object of this invention is to increase the number of situationsin which a GPS-based position location system may be utilized.

It is a further object of the present invention to employ GPS signals ina position location system which is not limited to use in only open andunobstructed areas.

Still another object of the present invention is to employ GPS-typesignals in a position location system.

It is still a further object of the present invention to preciselylocate by use of a GPS signal, an object positioned within an interiorspace.

Yet another object of the present invention is to precisely locate astationary or moving object contained within a shielded environment byuse of a GPS-type signal.

An additional object of the present invention is to precisely locate byuse of a GPS signal, an object positioned within a shielded environment.

Yet a further object of the present invention is to precisely locate asa function of time, an object positioned within an interior space by useof a GPS-type signal.

It is yet a further object of the present invention to remotely detectthe precise location of an object or person positioned within theinterior of a large structure such as a multi-floor office building, afactory or warehouse, a manufacturing or processing facility such as ashipbuilding yard or oil refinery, or also so positioned in a sea goingvessel or space craft.

Yet another additional object of this invention is to remotely detectthe precise location of a person moving about within a theme park,amusement park, or other expansive tourist area that may be shieldedfrom standard GPS signals to thereby assist the person in reaching adesired destination.

Still yet another object of the present invention is to utilizepseudosatellites to broadcast a corresponding GPS or GPS-type signalwithin an interior space or a shielded environment.

It is yet still another additional and further object of the presentinvention to precisely locate by use of a GPS or GPS-type signal, anobject or person moving between an interior space or shieldedenvironment and unobstructed open space.

These and other objects are attained in accordance with the presentinvention wherein there is provided a location positioning system foruse in a shielded environment. The system includes a GPS receiver forreceiving GPS signals and transmitting navigational data, a clockrecovery unit for receiving the navigational data and reconstructing anaccurate clock signal, a computer processing unit for receiving theaccurate clock signal and the navigational data, and at least fourpseudosatellites positioned within the shielded environment. One of theat least four pseudosatellites is non-coplanar relative to the others.The computer processing unit generates a respective GPS-type signalcorresponding to each of the at least four pseudosatellites, and therespective GPS-type signal contains new orbital parameters for eachcorresponding pseudosatellite. According to one aspect of thisinvention, the GPS-type signals are transmitted into the shieldedenvironment to be received by a receiver device located therein. Thereceiver device is capable of transmitting a location signal. In oneparticular implementation of this invention, there is further provided acomputer and a location receiver associated therewith. The locationreceiver is positioned within the shielded environment to receive thelocation signal from the receiver device so that a precise position ofthe location receiver may be determined by the computer by processingthe location signal. According to a specific use of this invention, thelocation device includes a cellular phone or alternatively a badgecapable of being attached to a person moving within the shieldedenvironment.

According to another embodiment of the present invention there isprovided a personnel location and tracking system for use in awork-place environment. This embodiment includes a GPS receiver forreceiving GPS signals and transmitting navigational data; a clockrecovery unit for receiving the navigational data and reconstructing anaccurate clock signal; a computer processing unit for receiving theaccurate clock signal and the navigational data; at least fourpseudosatellites positioned within the work-place environment, one ofthe at least four pseudosatellites being non-coplanar relative to theothers, wherein the computer processing unit generates a respectiveGPS-type signal corresponding to each of the at least fourpseudosatellites, the respective GPS-type signal containing new orbitalparameters for each corresponding pseudosatellite; a receiver devicecarried by an individual moving within the work-place environment, thereceiver device capable of transmitting a location signal, the GPS-typesignals being transmitted into the work-place environment to be receivedby the receiver device; and computer means having a location receiverassociated therewith, the location receiver being positioned within thework-place environment to receive the location signal from the receiverdevice so that a precise position of the individual carrying thelocation receiver may be determined by the computer means by processingthe location signal.

In accordance with another embodiment of this invention, there isprovided an inventory location and tracking system for use in awarehouse storage facility. This embodiment includes a GPS receiver forreceiving GPS signals and transmitting navigational data; a clockrecovery unit for receiving the navigational data and reconstructing anaccurate clock signal; a computer processing unit for receiving theaccurate clock signal and the navigational data; at least fourpseudosatellites positioned within the warehouse storage facility, oneof the at least four pseudosatellites being non-coplanar relative to theothers, wherein the computer processing unit generates a respectiveGPS-type signal corresponding to each of the at least fourpseudosatellites, the respective GPS-type signal containing new orbitalparameters for each corresponding pseudosatellite; and a receiver deviceattached to a respective item of inventory in warehouse storagefacility. This receiver device is capable of transmitting a locationsignal and the GPS-type signals are transmitted into the warehousestorage facility to be received by the receiver device. This embodimentfurther includes a computer having a location receiver associatedtherewith, the location receiver being positioned within the warehousestorage facility to receive the location signal from the receiver deviceso that a precise position of the respective item of inventory havingthe location receiver may be determined by the computer means byprocessing the location signal.

According to yet another embodiment of the present invention, there isalso provided a personal communications and location system for use inan indoor environment. This system similarly includes a GPS receiver forreceiving GPS signals and transmitting navigational data; a clockrecovery unit for receiving the navigational data and reconstructing anaccurate clock signal; a computer processing unit for receiving theaccurate clock signal and the navigational data; at least fourpseudosatellites positioned within the indoor environment, one of the atleast four pseudosatellites being non-coplanar relative to the others,wherein the computer processing unit generates a respective GPS-typesignal corresponding to each of the at least four pseudosatellites, therespective GPS-type signal containing new orbital parameters for eachcorresponding pseudosatellite; a receiver device in combination with acellular phone carried by an individual moving within the indoorenvironment, the receiver device capable of transmitting a locationsignal, the GPS-type signals being transmitted into the indoorenvironment to be received by the receiver device; and a computer havinga location receiver associated therewith. The location receiver ispositioned within the indoor environment to receive the location signalfrom the receiver device so that a precise position of the individualcarrying the location receiver may be determined by the computer byprocessing the location signal. The cellular phone thus providing apersonal communication link with an operator of the computer.

In still yet a further embodiment of this invention there is provided acombined positioning system for locating an object moving between ashielded environment and unobstructed open space. This system includes aplurality of global positioning satellites in orbit around the Earth,each of the global positioning satellites broadcasting a standard GPSsignal; a first GPS receiver for receiving the standard GPS signals andtransmitting navigational data; a clock recovery unit for receiving thenavigational data and reconstructing an accurate clock signal; acomputer processing unit for receiving the accurate clock signal and thenavigational data; at least four pseudosatellites positioned within theshielded environment, one of the at least four pseudosatellites beingnon-coplanar relative to the others, wherein the computer processingunit generates a respective GPS-type signal corresponding to each of theat least four pseudosatellites, the respective GPS-type signalcontaining new orbital parameters for each correspondingpseudosatellite; a receiver device attached to the moving object, thereceiver device capable of transmitting a location signal, the GPS-typesignals being transmitted into the shielded environment to be receivedby the receiver device; and a computer having a location receiverassociated therewith, the location receiver being positioned within theshielded environment to receive the location signal from the receiverdevice so that a precise indoor position of the moving object having thelocation receiver may be determined by the computer means by processingthe location signal when the object is within the shielded environment.This embodiment is also provided with a second GPS receiver attached tothe moving object, the second GPS receiver for receiving the standardGPS signals when the object is in the unobstructed open space so that aprecise outdoor position of the moving object having the second GPSreceiver may be obtained.

Yet another embodiment of this invention is directed to an interiorpositioning system having a GPS receiver for receiving GPS signals andtransmitting NAVDAT data, a clock recovery unit for receiving NAVDATdata and reconstructing an accurate clock signal, a computer forreceiving the accurate clock signal and the NAVDAT data, the computercapable of calculating pseudosatellite data for at least fourpseudosatellites, and the pseudosatellites capable of transmittingpseudosatellite data signals from the pseudosatellite data, wherein thepseudosatellite data signals are used for determining interior position.This embodiment may further include a second GPS receiver for receivingthe pseudosatellite data signals, the second GPS receiver being capableof using the pseudosatellite data signals to determine the interiorposition of the second GPS receiver, and a link for communicationbetween the second GPS receiver and the computer. This link may beimplemented as a duplex system capable of relaying the position of thesecond GPS receiver to the computer and capable of relaying informationfrom the computer to the second GPS receiver.

According to another aspect of this invention, there is provided amethod for providing an interior positioning system. This methodincludes the steps of receiving GPS signals, reconstructing an accurateclock signal from the GPS signals, calculating orbital parameters for atleast four pseudosatellites, and transmitting pseudosatellite datasignals using the reconstructed clock signal and orbital parameters forat least four pseudosatellites. This method may further includegenerating NAVDAT information from the received GPS signals, using theNAVDAT information for calculating the orbital parameters for thepseudosatellites, and adding offsets to the NAVDAT information whencalculating the orbital parameters, as well as delaying thereconstructed clock signal to account for different propagation time toeach of the pseudosatellites.

In accordance with yet another aspect of this invention there isprovided an interior positioning system having positional data regardingthe physical position of at least four pseudosatellites, a clock unitfor providing an accurate clock signal, a computer for calculatingpseudosatellite data derived from the positional data and the clocksignal, and a transmitter in communication to the computer fortransmitting pseudosatellite data signals derived from thepseudosatellite data. This embodiment may further include a second GPSreceiver for receiving the pseudosatellite data signals, the second GPSreceiver being capable of using the pseudosatellite data signals todetermine its interior position. In one particular implementation ofthis embodiment, there is further provided a link for communicationbetween the second GPS receiver and the computer. This link may take theform of a duplex system capable of relaying the position of the secondGPS receiver to the computer and capable of relaying information fromthe computer to the second GPS receiver.

According to yet another embodiment of the method of this invention thefollowing steps are practiced. First, providing positional informationregarding at least four pseudosatellites, then providing an accuratetime signal, also calculating pseudosatellite data for eachpseudosatellite by using the position information, and furthertransmitting the pseudosatellite data and the accurate time signal, thetransmitting of the accurate time signal being delayed for eachpseudosatellite to account for propagation delay.

BRIEF DESCRIPTION OF THE DRAWING

Further objects of the present invention together with additionalfeatures contributing thereto and advantages accruing therefrom will beapparent from the following description of certain preferred embodimentsof the present invention which are shown in the accompanying drawingwith like reference numerals indicating like components throughout,wherein:

FIG. 1 is a graphical representation of a prior art Global PositioningSystem;

FIG. 2 is a graphical representation of one embodiment of the interiorpositioning system according to the present invention;

FIG. 3 is a graphical representation of another embodiment of theinterior positioning system according to this invention;

FIG. 4 is graphical representation of yet another embodiment of theinterior positioning system according to the teaching of the presentinvention;

FIG. 5 is a block diagram of hardware employed in conjunction with theinterior positioning system of this invention;

FIG. 6 is a flow chart of software used in conjunction with the presentinterior positioning system;

FIG. 7 is a block diagram showing the overall structure of oneembodiment of the interior positioning system according to thisinvention;

FIG. 8 is a detailed block diagram further illustrating the clockrecovery unit discussed in conjunction with FIG. 7;

FIG. 9 is a detailed block diagram directed to the modulator as employedin connection with the present invention;

FIG. 10 is a detailed graphical representation of the structure havingan interior positioning system according to this invention as presentedin Example 1 below; and

FIG. 11 is a block diagram similar to that of FIG. 7, showing theoverall structure of another embodiment of the interior positioningsystem according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawing and initially to FIG. 1, there is shown aglobal positioning system 10 according to the prior art. The system 10is illustrative of the currently operating NAVSTAR Global PositioningSystem which includes many satellites represented by satellites 12-26orbiting the Earth 28. A total of twenty-four (24) are actually used.The orbiting satellites 12-26 communicate or broadcast signals 30-44,respectively, to the Earth 28. The signals 30-44 contain two types ofinformation. The first type of information is precise time encodedinformation and the second is extremely accurate encoded positioninformation. A GPS receiver located at position 45, for example, is ableto determine its exact location by measuring the difference between anyfour GPS signals and calculating the spatial distance or range to eachsatellite. The receiver then uses this data and the known position ofeach satellite to determine its own position in space, or on the surfaceof the earth. The NAVSTAR Global Positioning System is more fullydescribed in Aviator's Guide to GPS by Bill Clarke and The NAVSTARGlobal Positioning System by Tom Logsdon, the teachings of which areherein recognized to comprise part of the prior art related hereto. Thecurrent GPS system, however, does not function in many situations. Suchsituations include, for example, locations within a building structure,inside an urban environment having a variety of tall structures, underwater, inside dense forests, and underground. Turning now to FIG. 2,there is shown one embodiment of an internal positioning system 46according to the present invention. The illustration of FIG. 2 shows abuilding 47 having a first room 48, a second room 50, and a third room52. Three different uses of the interior positioning system 46 areillustrated in FIG. 2. These different uses will be briefly describedbefore further discussing in detail the specific components of theinterior positioning system 46.

In the first use, a badge 64 is enabled to determine its internalposition. The badge 64 may be provided with an optional transmitter (notshown) to report the badge position. In the second use, a pointer 66 isenabled to relate its internal position to the position of another knownobject such as a television set 68. By establishing the relativeposition of two objects, a pointing vector may be determined. In thethird use, a cellular phone 70 is shown as being enabled to determineits location with precise accuracy and use that location information tobeneficial advantage.

In connection with the third use discussed above, it is currentlycontemplated that satellites will soon be able to perform spot beamsearches for specific phones in specific cellular regions. For such anadvanced roaming cellular phone system to function appropriately, acellular phone must be able to determine its position and communicatethis information when activated in an entirely different area. In thismanner, a Los Angeles based cellular phone could be used in New YorkCity. The cellular phone 70 is herein currently enabled to function inthis manner. When the self-locating cellular phone 70 is activated inNew York City, the cellular phone 70 reports its interior or exteriorposition and thereby activates a new local area. There are thus proposedherein various configurations of internal positioning system receiversaccording to the present invention. The cellular phone 70, for example,contains a standard GPS receiver which is provided with an interface tothe cellular phone function. The badge 64 and the pointer 66 may containa more specialized receiver which responds to multiple messagescontained in the GPS-type signal described below. These messages cancontain specialized information, such as street address, zip codes, areacodes and the like, to enable more specific system functions.

With continuing reference to FIG. 2, the GPS satellites 16-22, forexample, direct GPS signals 34-40, respectively, toward the building 47.The signals 34-40 are communicated to a receiving and distributionsystem 54. The receiving and distribution system 54 distributescorresponding GPS-type signals to internal antennas or pseudosatellites56-62, one of each being positioned in each of the rooms 48-52 asillustrated. The embodiment of the interior positioning system 46 shownin FIG. 2 employs four channels which transmit new RF GPS-type signalsmodulated with orbital data corresponding to the actual location ofpseudosatellites 56-62. The form of the modulation is identical to theform of a standard GPS signal. The specific data contained is developedinternally by the internal positioning system 46. The receiving anddistribution system 54 makes appropriate changes to each of thesesignals to allow for positional offset. An example of positional offsetis discussed below in conjunction with FIG. 10.

The rooms 48-52 are preferably electronically isolated from each other.This ensures that interior positioning system signals from any one roomdo not transmit into another room. When the rooms 48-52 are notelectronically isolated from each other, only one set ofpseudosatellites 56-62 is required. Alternatively, it is contemplated toshare a pseudosatellite or any combination thereof between two or moredifferent rooms. This aspect of the present invention is illustrated bypseudosatellite 62 being shared between the two rooms 50 and 52, asillustrated in FIG. 2. This type of sharing is possible even when thetwo rooms are electronically isolated from each other. The internalpositioning system 46 may be implemented in any single or multiple roomstructure as long as the RF carrier frequency, or other carrierfrequency, can penetrate the walls. In addition, the fourpseudosatellites are preferably positioned in the room in oppositediagonal corners to maximize the distances therebetween so as to inturn, maximize the accuracy of the positioning capabilities of theinternal positioning system 46.

As shown in FIGS. 2 and 3, the badge 64 and cellular phone 70 areenabled to determine their interior position using a standard GPSreceiving antenna 78, and the receiving and distribution system 54 asnext described in detail.

The distribution system 54 is provided with a computer processing unit55 that converts each of the standard GPS signals 34-40 into acorresponding or interior GPS-type signal that includes the GPS timecomponent and a position component with new orbital parameters. Thisprocessing will be described in further detail below. The GPS-typesignals generated by the processing unit 55 are each hard-wired into arespective and corresponding pseudosatellite. Thus, the new orbitalparameters generated by the processing unit 55 relate to the exactphysical location of each corresponding pseudosatellite relative to theroom in which it is positioned. The present internal positioning system46 requires a minimum of four GPS satellites each emitting a standardGPS signal, and a related minimum of four corresponding pseudosatelliteseach receiving over hard wire, a modulated GPS-type signal provided bythe processing unit 55. Of the minimum of four corresponding pseudosatellites required by the internal positioning system 46, onepseudosatellite thereof must be non-coplanar relative to the others.This requirement is illustrated in FIGS. 2 and 3 by pseudosatellite 62being positioned in non-coplanar relation to the pseudosatellites 56,58, and 60.

In continuing description of the internal positioning system 46, each ofthe pseudosatellites 56, 58, 60, and 62 produces a respective signal 57,59, 61, and 63 which is transmitted into a respective electronicallyisolated room. The badge 64 and cellular phone 70 are each provided witha receiver capable of receiving the signals 57, 59, 61, and 63. Thebadge 64 and cellular phone 70 are in turn enabled to transmit theirexact position back to a computer system 72 equipped with a receiverantenna 73. The computer system 72 is provided with processing softwarecapable of computing the precise location of the badge 64 or thecellular phone 70 relative to its localized internal or shieldedenvironment. This location information may be printed-out or displayedon a monitor in any desired form such as floor and room number. Inaddition thereto, it is herein contemplated that a customized grid foreach specific environment, building, or area can be developed andprogramed into the computer system software so that output location datamight be presented in terms of known zones, sectors, or other chartingor surveying coordinates. Thus in this use, an operator of the computersystem 72 can determine the location of people internal to a buildingwho are equipped with either the badge 64 or the cellular phone 70. Inthe case of an individual carrying the phone 70, the computer operatormay rapidly communicate with them on an individual basis.

It is to be understood that the present invention is not limited to usewith the badge 64 or cellular phone 70, but rather may be used inconjunction with a pager, a portable computer, a personal digitalassistant, a watch, a robot, inventory, or numerous other stored objectsor items customarily carried by individuals moving within a particularenvironment. In addition thereto, it should be appreciated that notevery room requires a computer system 72. In the embodiments wherein therooms are electronically isolated, each such room is provided with areceiver 73. In this situation, all of the receivers 73 are connected toa single computer system 72 which may be placed in any desiredlocation--even locations miles or hundreds of miles away from thebuilding or environment in which the internal positioning system 46 isinstalled.

Referring now to FIG. 4, the pointer 66 is shown in relationship to thetelevision 68 in greater detail. Prior hereto, various devices have beenproposed for interactive use with a television. Such devices includetouch sensitive screens, mouse-type control devices, remote controldevices, and others. This use of the internal positioning system 46relates the pointer 66 to the television 68. The pointer 66 ispreferably a receiver with orientation determining capabilitiesprovided, for example, by a gyroscope. By determining the location ofthe television 63 and the pointer 66 in the manner described above, apointed-to-location 80 can be realized. This pointed-to-location can beadvantageously used in interfacing with television images.

FIG. 5 shows the hardware for the receiving and distribution system 54.The antenna 78 is used for receiving the GPS signals 30-44. The antenna78 then communicates with a power amplifier 82 which is used to amplifyand retransmit the signals to a receiver 84. The receiver 84 is used toselect the appropriate GPS channels for demodulation, decoding, andcalculation of time and navigational data (NAVDAT). The GPS receiver 84is used to determine the position of the receiving antenna 78. Thecomputer processing unit 55 is used to manage the signals from amultiplexer 96, a frequency converter 98, and a frequency divider 102. Adifferential GPS reference receiver 112 is used to perform differentialGPS calculations in any embodiment of the internal positioning system 46that may be in relative motion to the Earth 28. Higher resolution andaccuracy can be realized through use of differential GPS over time.According to this method of operation, the position of each system iscompared and the sum of the comparison of a larger number ofmeasurements averages out to give a more accurate reference position.

The processing accomplished in the receiving and distribution system 54by the computer processing unit 55, includes computing and multiplexingthe positional offset, registering movement, and recording a history ofeach badge 64 or cellular phone 70. This processing also includesdifferential GPS information when required by the internal positioningsystem 46. The preferred processing software is shown in the flow chartof FIG. 6. Additional aspects of FIG. 5 will be discussed in furtherdetail below in conjunction with FIG. 7.

With reference now to FIG. 6, one embodiment of software used to run theinternal positioning system 46 is shown. It should be understood thatvarious other features and embodiments of the software are possible foruse with the internal positioning system 46, and that the followingembodiment is an illustrative, non-limiting example thereof. In thisembodiment, the processing starts with the initialization block 122. TheGPS receiver 84 and differential GPS receiver 112 are initialized andcalibrated in blocks 124 and 126. A report status software block 128accepts the status from the GPS receiver 84 and the differential GPSreceiver 112, and then collaborates data and interacts with a fileholding information regarding previous history files of a particularbadge 64 or cellular phone 70. A boot history file 132 contains updatedpositions on transition activity that has taken place since the reportstatus was last generated. A poll control panel function block 134drives a data display number 136 which functions as an operator controlmonitoring station that displays positional location of various objects.A registered movement tag file block 138 interacts with a file block 140to continuously monitor position locations. A look-up software module142 interacts with the operating system of the computer processing unit55. Software blocks or modules 144 and 146 record changes to a historyfile on the internal positioning system 46. This system history file ispreferably maintained so as to determine location. Block 148 is optionaland used for differential GPS processing of information received formthe differential receiver 112 when employed as required by a specificsystem implementation. A receive update block 150 receives an updatedposition from differential GPS receiver 112. A transmit data block 152transmits the processed data to a desired location.

Referring to FIG. 7, there is shown a particular group of the satellites16-22 having the corresponding standard GPS satellite signals 34, 36,38, and 40 as discussed above in conjunction with FIGS. 1 and 2. Each ofthe satellites 16-22 broadcasts its own unique coded messagecontinuously. The corresponding satellite signals 34-40 each have amessage structure containing three basic components.

The first of these three basic components is a Coarse Acquisition codesignal, or C/A code. This coarse acquisition code signal is a 1.023 MHzcarrier that is phase modulated using binary phase shift keying, orBPSK, by the pseudorandom code assigned to each of the satellites 16-22.The pseudorandom code is a fixed series of binary bits having a lengthof 1,023 bits. Each satellite 16-22 broadcasts using an assigned andspecific code algorithm. The code algorithms are well defined in GPSrelated literature.

The second of the three basic components of the standard GPS signal is aPrecision code signal, or P code. The precision code is BPSK modulatedat 10.23 MHz. This precision code is a pseudorandom code and issignificantly long containing specific satellite identification datasimilar to the C/A code.

Lastly, the third basic component of a GPS signal is satellite data.This satellite data modulates both the precision code and the coarseacquisition code at 50 bits per second, again using BPSK modulation. Thesatellite data includes several information categories, the mostpertinent being ephemeris data for each GPS satellite. Ephemeris datadescribes the orbital path of the satellite in terms defined by theInertial Coordinate System. The Inertial Coordinate System is based onEarth's center of gravity or COG, in which the North Celestial poledefines a Z axis through the COG, and the plane of the Celestial Equatoris perpendicular to the Z axis and intersects the COG. The orbitalparameters of the satellite are defined in terms of right ascension,inclination, argument of perigee, semi-major axis, and eccentricity, aswell as specific parameters of time and mean anomaly. Almanac data forall satellites is also included in the satellite data.

The GPS receiver 84 as shown in FIG. 7, computes precise locationinformation by using the satellite signals 34-40. The GPS receiver 84computes its own location using data from at least four satellites16-22. Additional satellites which are in view, however, willnecessarily add to the data from which the GPS can select the minimum offour signals. The GPS receiver 84 determines the pseudorange to eachsatellite and solves for the user, a position in terms of latitude,longitude, and altitude. The pseudorange measurement has two principalsources of inaccuracy. These include the clock timing error andpropagation variations. The GPS receiver 84 outputs a NAVDAT data signal164 via an RS422 serial data port. The NAVDAT data signal 164 containsnavigational data and GPS almanac data. This navigational data includeslatitude, longitude, altitude, and time of day. The GPS almanac dataincludes GPS week number, satellite health, and almanac ephemeris data.

With continuing reference now to FIGS. 5 and 7, a clock recovery unit106 receives NAVDAT data signal 164 which includes a coarse time signaland a receiver clock oscillation signal. The clock recovery unit 106outputs a precision clock signal 166 at 10.23 MHz clock which has aprecision equivalent to the atomic clock standard.

The computer processing unit 55 utilizes the precision clock signal 166and the NAVDAT data signal 164 in addition to data supplied by anoperator. This additional data assists in defining the physical offsetsof each pseudosatellite location. One aspect of this invention is totransmit the GPS-type signal of satellite information from each of thepseudosatellites or antenna 56-62. In view thereof, these antenna areherein considered to be "pseudosatellites" since the standard GPS signalhas been modified to contain new orbital information relating to theorbit of each pseudosatellite around the Earth. The physical offset andtime offset, which are covered in greater detail in discussion relatingto FIG. 10 are added by the computer processing unit 55. GPS-typesignals 168, 170, 172, and 174 are, respectively, the coarse acquisitioncode, the precision code, and the satellite data for each of thepseudosatellite 56, 58, 60, and 62. A modulator 86 combines thesesignals using BPSK modulation and regenerates the RF carrier.Pseudosatellite data signals 176, 178, 180, and 182 are the respectivedriver signals for the pseudosatellites 56, 58, 60, and 62.

The clock recovery unit 106 employed in conjunction with the presentinvention is shown in greater detail in FIG. 8. The clock recovery unit106 receives the NAVDAT data signal 164 from the GPS receiver 84. Theclock recovery unit 106 generates the precision clock signal 166 whichhas an accuracy equivalent to the atomic clock standard. The clockrecovery unit 106 provides frequency synthesis at 10.23 MHz using aconventional phase lock loop. Several commercially available GPSaccessories will perform the functions required by the clock recoveryunit 106. The Hewlett Packard 58503A, for example, will provide theprecision clock signal 166.

Further aspects of the modulators 86 will now be described in detailwith reference to FIG. 9. The computer processing unit 55 generates theGPS-type output signals 168, 170, 172, and 174 which contain coarseacquisition code, precision code, satellite data, and the precisionclock signal 166. The precision clock signal 166 is multiplied by thenumber 154 in the multiplier block 184 to produce an L1 carrier signal186. The P code, satellite data code, and coarse acquisition code areprocessed through exclusive-OR circuitry 190 to produce BPSK outputsignals 192 and 194. The BPSK output signal 192 and the L1 carriersignal 186 are combined in an RF modulator 196 to produce a signal 198.The BPSK output signal 194 and a phase shifted signal stemming fromsignal 184, are combined in an RF modulator 197 to produce signal 200.As shown in FIG. 9, the signals 198 and 200 are summed to produce thepseudosatellite data driver signal 176 corresponding to pseudosatellite56. Satellite data contained in this GPS-type signal contains ephemerisdata which describes the orbit of the pseudosatellite in terms that thestandard GPS receiver can use in its calculations. Additionally, thesatellite data contains any special messages required for the specificsystem.

A specific example of the internal positioning system 46 will now bepresented and described with reference with FIG. 10.

EXAMPLE 1

FIG. 10 shows a detailed example of the interior positioning system 46in a hypothetical room 204 having a width w of 200 meters, a length I of300 meters, and a height h of 20 meters. This hypothetical room 204 haswalls which parallel north, south, east, and west, and uses the interiorpositioning system 46 having coaxial cable with a propagation velocityof 0.6. In this example, the latitude, longitude, and altitudecoefficients for pseudosatellites 56, 58, 60, and 62 as well as the timedelay will be calculated. Pseudosatellite 56 is a distance of 5 meterssouth of the receiving and distribution system 54 in the upper portionof the southwest corner of room 204 and on the same altitude with theGPS receiving and distribution system 54. Pseudosatellite 58 is locateda distance of 295 meters north of the GPS receiving and distributionsystem 54 and a distance of 20 meters therebelow. The coaxial cableattached to pseudosatellite 58 is 315 meters long. Pseudosatellite 60 isa distance 295 meters north, 200 meters east, and level with respect toGPS receiving and distribution system 54. Pseudosatellite 60 has acoaxial cable of 495 meters connecting it to the receiving anddistribution system 54. Pseudosatellite 62 is 5 meters south, 200 meterseast, and 20 meters below the receiving and distribution system 54.Pseudosatellite 62 is connected with a 225 meter coaxial cable. Thelength of antenna cable 206 does not affect the operation of theinterior positioning system 46 because the resulting uniform clock biaswhich appears on each channel is canceled. Thus the NAVDAT from the GPSreceiver 84, FIG. 5, contains the correct antenna location. Since theGPS receiver 84 is directly below the antenna 78, no additional latitudeor longitude correction is required. For the antenna 78, being hereinpositioned 30 meters above the receiving and distribution system 54,there is imposed a fixed altitude offset of -30 meters on eachpseudosatellite 56, 58, 60, 62. The pseudosatellites 56, 58, 60, and 62are displaced in three dimensions expressed in terms of latitude,longitude, and altitude with reference to the antenna 78. These actualdistances are readily measured. The angular offsets are used tocalculate orbit parameters which are transmitted in the satellite dataemanating from pseudosatellites 56-62. These angular offsets arecalculated using a conversion to angular measure. Furthermore the timedelay is calculated with respect to cable length and propagationcoefficient. The time delays are used to control the time that thecomputer sends each frame of data. For instance, the time delay for a200 meter coaxial cable will be longer than that for a 100 meter coaxialcable of the same type. In this case, the computer processing unit 55transmits the data frame for the 200 meter coaxial cable earlier thanthat for the 100 meter coaxial cable. The time delay for use of variouslengths of each element of coaxial cable is similarly time-controlled bythe computer processing unit 55. The specific offsets for thehypothetical room 204 of FIG. 10 are set out in Table 1 below.

                  TABLE 1                                                         ______________________________________                                        Pseudosatellite                                                                             56       58      60     62                                      ______________________________________                                        Latitude, minutes of arc                                                                    -.000548 0.0323  0.0323 -0.000548                               Longitude, minutes of arc                                                                   0        0       0.002646                                                                             0.002646                                Altitude, meters                                                                            -30      -50     -30    -50                                     Time Delay, nanoseconds                                                                     2.775    174.825 274.725                                                                              124.875                                 ______________________________________                                    

Based upon these offsets, the computer formulates the parameters foreach pseudosatellite 56, 58, 60, and 62 by a specific method. Thismethod includes the following steps:

1. Convert latitude, longitude, altitude, and time to internalpositioning system ephemeris data format;

2. Store data in allocated registers for delayed retransmission tooutputs;

3. Assign pseudorandom code numbers and compute orbital parameters;

4. Add other internal positioning system formatted data, includingtelemetry, hand over word, as required by each conventional receiver;and

5. Assign additional data to each pseudosatellite data word forspecialized receiver functions.

With reference now to FIG. 11, another embodiment of the internalpositioning system 46 will be discussed in detail. In this embodiment,the GPS receiving antenna 78, the power amplifier 82, and the GPSreceiver 84 are eliminated. In place of using the standard GPS signals30-44, the positions of each pseudosatellite 56, 58, 60 and 62 isinputted directly to the computer processing unit 55 in terms oflatitude, longitude, and altitude. This data may be derived, forexample, from surveyor's measurements. The clock recovery unit 106 wouldbe replaced by a precision clock. Standard precision clocks such as anatomic clock, a WWV clock, or United States Naval Observatory basedclock may be used. In this embodiment without the GPS receiver 84, thecomputer operator supplies the positional data to the computerprocessing unit 55 directly. The remaining operations for the processingunit 55 and the pseudosatellites 56-62 are the same as described above.

While this invention has been described in detail with reference tocertain preferred embodiments, it should be appreciated that the presentinvention is not limited to those precise embodiments. Rather, in viewof the present disclosure which describes the current best mode forpracticing the present invention, many modifications and variationswould present themselves to those of skill in the art without departingfrom the scope and spirit of this invention. The scope of this inventionis, therefore, indicated by the following claims rather than by theforegoing description. All changes, modifications, and variations comingwithin the meaning and range of equivalency of the claims are to beconsidered within their scope.

What is claimed is:
 1. A location positioning system for use in ashielded environment, said system comprising:a GPS receiver forreceiving GPS signals having navigational data encoded therein; a clockrecovery unit that constructs a clock signal using said navigationaldata, wherein said clock signal accurately represents a local time; acomputer processing unit for receiving said clock signal and saidnavigational data; and at least four pseudosatellites positioned withinthe shielded environment, one of said at least four pseudosatellitesbeing non-coplanar relative to the others, wherein said computerprocessing unit generates a respective GPS-type signal corresponding toeach of said at least four pseudosatellites, said respective GPS-typesignal containing new orbital parameters for each correspondingpseudosatellite.
 2. The location positioning system according to claim 1wherein said GPS-type signals are transmitted into the shieldedenvironment to be received by a receiver device located therein, saidreceiver device capable of transmitting a location signal.
 3. Thelocation positioning system according to claim 2 further includingcomputer means and a location receiver associated therewith, saidlocation receiver being positioned within said shielded environment toreceive said location signal from said receiver device so that a preciseposition of said location receiver may be determined by said computermeans by processing said location signal.
 4. The location positioningsystem according to claim 2 wherein said location device includes acellular phone.
 5. The location positioning system according to claim 2wherein said location device includes a badge capable of being attachedto a person moving within the shielded environment.
 6. A personnellocation and tracking system for use in a work-place environment, saidsystem comprising:a GPS receiver for receiving GPS signals andtransmitting navigational data; a clock recovery unit for receiving saidnavigational data and reconstructing an accurate clock signal; acomputer processing unit for receiving said accurate clock signal andsaid navigational data; at least four pseudosatellites positioned withinthe work-place environment, one of said at least four pseudosatellitesbeing non-coplanar relative to the others, wherein said computerprocessing unit generates a respective GPS-type signal corresponding toeach of said at least four pseudosatellites, said respective GPS-typesignal containing new orbital parameters for each correspondingpseudosatellite; a receiver device carried by an individual movingwithin the work-place environment, said receiver device capable oftransmitting a location signal, said GPS-type signals being transmittedinto the work-place environment to be received by said receiver device;and computer means having a location receiver associated therewith, saidlocation receiver being positioned within the work-place environment toreceive said location signal from said receiver device so that a preciseposition of the individual carrying said location receiver may bedetermined by said computer means by processing said location signal. 7.An inventory location and tracking system for use in a warehouse storagefacility, said system comprising:a GPS receiver for receiving GPSsignals and transmitting navigational data; a clock recovery unit forreceiving said navigational data and reconstructing an accurate clocksignal; a computer processing unit for receiving said accurate clocksignal and said navigational data; at least four pseudosatellitespositioned within the warehouse storage facility, one of said at leastfour pseudosatellites being non-coplanar relative to the others, whereinsaid computer processing unit generates a respective GPS-type signalcorresponding to each of said at least four pseudosatellites, saidrespective GPS-type signal containing new orbital parameters for eachcorresponding pseudosatellite; a receiver device attached to arespective item of inventory in warehouse storage facility, saidreceiver device capable of transmitting a location signal, said GPS-typesignals being transmitted into the warehouse storage facility to bereceived by said receiver device; and computer means having a locationreceiver associated therewith, said location receiver being positionedwithin the warehouse storage facility to receive said location signalfrom said receiver device so that a precise position of the respectiveitem of inventory having said location receiver may be determined bysaid computer means by processing said location signal.
 8. A personalcommunications and location system for use in an indoor environment,said system comprising:a GPS receiver for receiving GPS signals andtransmitting navigational data; a clock recovery unit for receiving saidnavigational data and reconstructing an accurate clock signal; acomputer processing unit for receiving said accurate clock signal andsaid navigational data; at least four pseudosatellites positioned withinthe indoor environment, one of said at least four pseudosatellites beingnon-coplanar relative to the others, wherein said computer processingunit generates a respective GPS-type signal corresponding to each ofsaid at least four pseudosatellites, said respective GPS-type signalcontaining new orbital parameters for each correspondingpseudosatellite; a receiver device in combination with a cellular phonecarried by an individual moving within the indoor environment, saidreceiver device capable of transmitting a location signal, said GPS-typesignals being transmitted into the indoor environment to be received bysaid receiver device; and computer means having a location receiverassociated therewith, said location receiver being positioned within theindoor environment to receive said location signal from said receiverdevice so that a precise position of the individual carrying saidlocation receiver may be determined by said computer means by processingsaid location signal, said cellular phone providing a personalcommunication link with an operator of said computer means.
 9. Acombined positioning system for locating an object moving between ashielded environment and unobstructed open space, said systemcomprising:plurality of global positioning satellites in orbit aroundthe Earth, each of said global positioning satellites broadcasting astandard GPS signal; a first GPS receiver for receiving the standard GPSsignals and transmitting navigational data; a clock recovery unit forreceiving said navigational data and reconstructing an accurate clocksignal; a computer processing unit for receiving said accurate clocksignal and said navigational data; at least four pseudosatellitespositioned within the shielded environment, one of said at least fourpseudosatellites being non-coplanar relative to the others, wherein saidcomputer processing unit generates a respective GPS-type signalcorresponding to each of said at least four pseudosatellites, saidrespective GPS-type signal containing new orbital parameters for eachcorresponding pseudosatellite; a receiver device attached to the movingobject, said receiver device capable of transmitting a location signal,said GPS-type signals being transmitted into the shielded environment tobe received by said receiver device; computer means having a locationreceiver associated therewith, said location receiver being positionedwithin the shielded environment to receive said location signal fromsaid receiver device so that a precise indoor position of the movingobject having said location receiver may be determined by said computermeans by processing said location signal when the object is within theshielded environment; and a second GPS receiver attached to the movingobject, said second GPS receiver for receiving the standard GPS signalswhen the object is in the unobstructed open space so that a preciseoutdoor position of the moving object having said second GPS receivermay be obtained.
 10. An interior positioning system comprising:a GPSreceiver for receiving GPS signals and transmitting NAVDAT data; a clockrecovery unit for receiving NAVDAT data and reconstructing an accurateclock signal; a computer for receiving the accurate clock signal and theNAVDAT data, said computer capable of calculating pseudosatellite datafor at least four pseudosatellites, and the pseudosatellites capable oftransmitting pseudosatellite data signals from the pseudosatellite data,wherein the pseudosatellite data signals are used for determininginterior position.
 11. The interior positioning system of claim 10further comprising a second GPS receiver for receiving thepseudosatellite data signals, said second GPS receiver being capable ofusing the pseudosatellite data signals to determine the interiorposition of the second GPS receiver.
 12. The interior positioning systemof claim 11 further comprising means for communication between thesecond GPS receiver and the computer.
 13. The interior positioningsystem of claim 12 wherein said means for communication is a duplexsystem capable of relaying the position of the second GPS receiver tothe computer and capable of relaying information from the computer tothe second GPS receiver.
 14. A method for providing an interiorpositioning system comprising the steps:receiving GPS signals;reconstructing an accurate clock signal from the GPS signals;calculating orbital parameters for at least four pseudosatellites; andtransmitting pseudosatellite data signals using the reconstructed clocksignal and orbital parameters for at least four pseudosatellites. 15.The method for providing an interior positioning system of claim 14further comprising the steps:generating NAVDAT information from thereceived GPS signals; using the NAVDAT information for calculating theorbital parameters for the pseudosatellites; and adding offsets to theNAVDAT information when calculating the orbital parameters.
 16. Themethod for providing an interior positioning system of claim 6 furthercomprising the step of delaying the reconstructed clock signal toaccount for different propagation time to each of the pseudosatellites.